Eyring Reverberation Time (RT60, High Absorption)
RT60 by the Eyring-Norris equation: RT60 = 0.049 V / (-S ln(1 - a_bar)).
Example
You enter
- Room volume (ft³) 5000
- Total surface area (ft²) 1300
- Average absorption coefficient (0-1) 0.3
You get
- RT60 (Eyring) 0.53 s
- RT60 (Sabine, for comparison) 0.63 s
- Total absorption 390 sabins
Checked against published worked examples from: Eyring-Norris (low-absorption convergence to Sabine).
Details, formula, and sources
Scopea_bar = total sabins / total surface area - the form to use once a room is well treated. Sabine over-predicts once the room is well treated; Eyring models absorption per reflection and returns a shorter RT60 whenever a_bar is more than a few tenths -- a 5,000 ft^3 room with 1,300 ft^2 of surface at a_bar 0.30 is 0.53 s (Eyring) vs 0.63 s (Sabine), converging as a_bar -> 0. Use Eyring for studios and heavily treated spaces; Sabine for a quick live-room estimate. The acoustician and the venue govern.
Formula or tableRT60 = 0.049 x V / (-S x ln(1 - a_bar)), a_bar = total_sabins / S = A/S; Sabine RT60 = 0.049 x V / A for comparison.
Source and editionC.F. Eyring (Eyring-Norris) reverberation equation (J. Acoust. Soc. Am. 1930; public domain); the high-absorption companion to Sabine.
Free accessThe Eyring-Norris equation is public-domain acoustics; a_bar (the average absorption coefficient) and the surface area are the user's own room take-off, and the 0.049 imperial coefficient is an editable field.
What governsEstimate. AHJ and licensed professional govern.
API field namesvolume_ft3, surface_area_ft2, avg_absorption, rt60_eyring_s, rt60_sabine_s, total_sabins
- Eyring-Norris equation RT60 = 0.049 V / (-S ln(1 - a_bar)); reduces to Sabine as a_bar -> 0Eyring (1930)
- Average absorption a_bar = total sabins / total surface area, 0 < a_bar < 1room acoustics
- When to use Eyring for high-absorption (well-treated) rooms; Sabine over-predicts thereacoustics practice